Can you tell if a man is dangerous just by looking at his face?

Now some of the “new physiognomists” are resurrecting an old claim: that you can gauge a man’s penchant for aggression by the cut of his jib. Last fall University of California-Santa Barbara psychologist Aaron Sell reported that college students could accurately estimate the upper body strength of unfamiliar men after viewing their faces alone. (The men’s necks were obscured.) The students did equally well with fellow undergraduates and men from South American indigenous groups—all of whom had had their strength measured using gym equipment. Interestingly, the toughest-looking undergrads also reported getting in the most fights. Another study by Sell suggests that such formidable men are more prone to use violence—or advocate military action—to resolve conflicts.

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So which features might hint at belligerence? Sell suspects the brow ridge and jaw, two structures that are shaped by testosterone in puberty. (High testosterone has been linked with masculine looks as well as with aggression.) Other scientists propose a different measure: the width-to-height ratio of the face, as measured from cheek to cheek and lip to brow. Last year, a team of Canadian psychologists showed that men with wider faces (think Ernie) score higher in lab tests of aggression than slender-faced men (think Bert). They also found that wide-faced hockey players rack up more penalty minutes. Now, two studies in Psychological Science—one from August and another forthcoming—reinforce the notion that stout-faced men appear tougher and are more likely to behave in aggressive and untrustworthy ways.

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The psychologist Robert Deaner recently went through the database of mug shots of the Michigan Department of Corrections and measured the facial width-to-height ratios of 688 white convicted criminals. He classified each inmate as either violent or nonviolent based on FBI standards and compared their faces with their crimes. There was no difference in the average width-to-height ratio of violent vs. nonviolent offenders, he says. However, Deaner did find that prisoners’ faces were significantly wider than a population of undergraduates. Curiously, pro hockey players had even wider faces than the prisoners. His conclusion: “Face width does not predict violent crime. … [W]e believe the cliché, ‘never judge a book by its cover’ remains sound advice.”